Woot originated as a hacker term for root (or administrative) access to a computer. However, with the term as coincides with the gamer term, "w00t".

"w00t" was originally an trunicated expression common among players of Dungeons and Dragons tabletop role-playing game for "Wow, loot!" Thus the term passed into the net-culture where it thrived in video game communities and lost its original meaning and is used simply as a term of excitement.

A word originating from the old D&D games, was used to express excitement when finding treasure, the player would say "Wow loot!" thus over time turning into "w00t" in the videogame world, as a form of satisfaction or victory..

It originated from back in the days of MUD games, after killing an opponent loot was a rare find, so if someone found loot they would say "wow loot!". This evolved into "woot" for short which further evolved to simply be a general exclamation of excitement.

Before ALL of that, woot was a happy noise made by certain Monkees and Guinea Pigs when they are happy or content. Net nerds like to take credit for creating stuff that they only adopted. But I know better. I've heard those monkets. And they're happy. woot.

Kristy walks in the door from a long day of work and her Guinea Pig, thrilled to see her, asks "Woot? Woot woot? Woot."